A stud and nut electrode welding electrode assemblies is shown in U.S. Pat. No. 3,504,159 commonly assigned with the present application. The electrode assembly includes a holder for a stud and nut electrode tip. One problem with such prior art tips is that the electrode includes a flat face that engages either the stud or nut having weld projections thereon that create points of resistance on the thin plate at which a weld nugget is produced to secure the stud or nut to the thin plate. Such projection welding applications impose a substantial loading on the electrode tip during the welding cycle. In order to increase the durability of such electrode configurations applicant has developed a ring shaped electrode hard copper tungsten material to reduce electrode wear in such projection welding applications. The holder includes an external cooling jacket that is arranged around the outer periphery of an electrode tip supported within a cavity formed within the holder that is suitable for use with all copper holders and electrode tips. However, in the case of high strength electrodes the alloys that provide such strength conduct less electricity during the welding cycle so that higher energy is required to produce welding current. The increased electrical energy is released as heat at the weld face. Such heat causes higher electrode temperatures that can result in expulsion that in turn will adversely affect the characteristics of the weld nugget that is formed between the projections on either the stud or the nut and the thin plate.
U.S. Pat. No. 3,558,847, also commonly assigned with the present application, discloses a welding electrode holder that holds two spaced electrodes in a manner that will balance the force contact therebetween. The '847 holder includes a water tube that directs inlet cooling water into a cavity formed within one electrode and thence through internal passages to a second electrode cavity for return through a water tube to an outlet orifices supported by the holder. While suitable for its intended purpose, the cooling system in the '847 patent is not configured to cool electrodes suitable for projection welding of studs and nuts to thin metal plates wherein a wear resistant, high conductivity ring type electrode builds up heat during welding cycles.